Magician-turned-mathematician uncovers 51% bias in coin flipping (2004)

Zoins

Interesting article for coin folks

https://news.stanford.edu/pr/2004/diaconis-69.html

Mr_Spud

Cool article. I thought it was going to be about people reselling sold out mint products, but it isn’t

bolivarshagnasty

Only made it half way through the article.........well, maybe 51%.

MrEureka

I wonder if it boils down to the center of weight of the coin not being at the exact center of the coin. If so, the odds could vary for each coin type!

CoinJunkie

I can't wait for the Super Bowl. I'm gonna kill my bookie!

Along

Well 51% of the time

BAJJERFAN

@MrEureka said:
I wonder if it boils down to the center of weight of the coin not being at the exact center of the coin. If so, the odds could vary for each coin type!

Just flip a planchet.

jmlanzaf

@MrEureka said:
I wonder if it boils down to the center of weight of the coin not being at the exact center of the coin. If so, the odds could vary for each coin type!

The article says that 51% of the time it comes up the same side as when it was flipped. So, oddly/interestingly, it is not a heads/tail bias it is a same/different bias.

I also say it is basically hogwash as he himself said that he learned to flip a coin so it comes up heads 10 out of 10 times. That indicates that the flipper has some control over the results. So the bias he records could simply be not having a completely random set of flippers.

MrEureka

The method of flipping could also be relevant. If catching the coin in the air, any bias would be more likely to show itself. If the coin lands on a hard surface, not so much.

ctf_error_coins

I'll bet on it landing on its edge ....

airplanenut

So that guy is really a mathemagician

MasonG

"Montgomery had developed the Falling Cat Theorem -- a theory that explains how a cat dropped from any angle always manages to land on its feet. Surely this expertise in angular momentum could also apply to falling coins, Diaconis thought."

So the guy thinks that how a living, breathing animal with senses that enable it to determine up from down lands would also apply to how a falling inanimate item would land?

I think he needs to think on this some more.

jmlanzaf

@MasonG said:
"Montgomery had developed the Falling Cat Theorem -- a theory that explains how a cat dropped from any angle always manages to land on its feet. Surely this expertise in angular momentum could also apply to falling coins, Diaconis thought."

So the guy thinks that how a living, breathing animal with senses that enable it to determine up from down lands would also apply to how a falling inanimate item would land?

I think he needs to think on this some more.

Are you saying the coins don't adjust themselves in mid-air?

MasonG

@jmlanzaf said:
Are you saying the coins don't adjust themselves in mid-air?

Well- to be honest, I haven't done exhaustive studies but I'm inclined to believe they don't.

jmlanzaf

@MasonG said:

@jmlanzaf said:
Are you saying the coins don't adjust themselves in mid-air?

Well- to be honest, I haven't done exhaustive studies but I'm inclined to believe they don't.

LOL. The whole article is a little odd. He says he can get 10 out of 10 heads flipping it intentionally and yet we're to believe there is some kind of meaningful statistics governing the motion of the coin.

He does sound like an interesting guy, though.

MasonG

@jmlanzaf said:
He says he can get 10 out of 10 heads flipping it intentionally...

I didn't notice anywhere in the article that he demonstrated this to anyone's satisfaction. Personally, I'm skeptical- but that's just me.

@jmlanzaf said:
The whole article is a little odd.

Indeed.

Sandman70gt

I cant believe I just spent the time to read that whole thing only to have learned its only 51%.
I was expecting something :unexpected.

bearcave

😂

ricko

Interesting article...Not so much for the subject/conclusion... But for how a high school dropout went from magician to professor of mathematics.... A real study in human endeavor. Cheers, RickO

WillieBoyd2

This happens all the time:

... in the Twilight Zone.

BStrauss3

The informal paper is here: https://statweb.stanford.edu/~susan/papers/headswithJ.pdf

And the peer-reviewed paper: https://www.jstor.org/stable/20453950, Published By: Society for Industrial and Applied Mathematics